1. Field
The present disclosure relates to an electric vehicle.
2. Description of the Related Art
Japanese Unexamined Patent Application Publication No. 2011-250555 discloses a wireless power transmission system where electric power transmission and charging are performed by electromagnetic coupling between an external power supply side coil, and a reception side coil within the vehicle. A reception device within the vehicle includes an impedance rectifier to adjust impedance of a resonance system made up of a transmitting resonator and a receiving resonator.
Japanese Unexamined Patent Application Publication No. 2011-250555 discloses, in paragraph 0060 and FIGS. 1 and 3, realizing efficient power transmission by the receiving device adjusting impedance of the impedance rectifier, based on electric power information. This electric power information is a detection value of reflected power received from the power transmission facility.
Japanese Unexamined Patent Application Publication No. 2012-182887 discloses a wireless power transmission system which performs charging from power transmission by magnetic coupling between a power supply side coil and a reception side coil. It is stated therein that power transmission efficiency changes depending on the charging power supplied from the power supply side to the reception side circuit, and the state of charge (SOC) of the battery, which indicates the amount of charge remaining (load voltage), so the secondary battery is charged in a state where power transmission efficiency is not very high.
Accordingly, Japanese Unexamined Patent Application Publication No. 2012-182887 proposes, in paragraphs 0010, 0011, and 0013, a wireless power transmission method and wireless power transmission device, including a process of detecting charging power, and a process to change the resistance ratio based on the detected charging power so that the power transmission efficiency between the power supply side coil and reception side coil will be high. This aims to solve the problem in which power transmission efficiency between the power supply side coil and reception side coil drops under constant voltage control, due to the charging power being reduced when switching from constant current control to constant voltage control to charge the secondary battery.